Paper article coated with a fatty amide slip coating



United States Patent 3,458,346 PAPER ARTICLE COATED WITH A FATTY AMIDE SLIP COATING Charles T. Mitchell, Jr., North Reading, and William F. Scheufele, South Natick, Mass., assignors to W. R. Grace 8: Co., Cambridge, Mass., a corporation of Connecticut No Drawing. Filed Feb. 10, 1966, Ser. No. 526,360 Int. Cl. D21h 1/40; B32b 27/10 U.S. Cl. 117-76 4 Claims ABSTRACT OF THE DISCLOSURE A paper substrate is coated with a moisture-resistant film (e.g., a vinylidene chloride polymer) and a slip coating comprising a C and C fatty amide (e.g., oleyl amide) deposited upon the film to provide a product particularly useful in making spiral-wound paper can bodies.

This invention relates to a composition suitable for use as a slip agent and which is particularly useful in the preparation of spiral-wound tubular paper cans.

Spiral-wound tubular paper cans have been adapted for packaging a number of materials. The spiral-wound tubes are made on a spiral winder. In brief, this machine consists of a stationary round steel mandrel over one end of which is looped an endless belt, while the other end has a traveling saw. The raw paper stock, i.e., flexible paperboard or paper of the type used in manufacturing paper cans, is slit into narrow rolls which are fed into the winder from either side.

Each web of paper passes over a glue roll and from there around the mandrel and under the endless belt at an angle of 45 to 60. The pressure of the moving belt causes the formed tube to rotate on the mandrel, thus drawing in more material and causing the formed tube to move forward in a helical motion along the mandrel. The continuous spiral tube may be cut to size on the winder or as a separate operation. The cut tubes are then placed in a press and the ends of the tube are flared to receive the cam end.

Paper cans are normally provided with a foil lining or a film or coating of a material which bars moisture penetration. Representative of the moisture barriers are coatings formed from vinylidene chloride polymers. These coatings, and moisture barrier materials in general, sufier from a lack of slip, i.e., the film-to-metal coeificient of friction is high. This is a serious handicap in the formation of paper cans because it results in jamming of automatic machinery and difliculty in removing the tubes from the mandrel.

In an actual operation, for example, the webs of paper are provided with a vinylidene chloride polymer coating. The coated webs are fed into the belt loop and wrapped around the mandrel. This action produces a great deal of frictional heat and galling, i.e., wearing away by friction, of the coating. The mandrel, if uncooled, will heat up to a temperature of 200 F. and the coating will adhere to the mandrel causing a shutdown and requiring cleaning and rethreading. A water cooled mandrel offers a slight improvement in that the temperature can be kept below 150 F., but galling still occurs. The desired winding speed of 300 to 1,000 feet per minute requires a slip coat of some type even on foiled lined cans.

Various agents of different types have been proposed for use as slip agents, but most of the materials of the prior art have had one or more defects which detract from their usefulness on a practical commercial scale. Some do not impart the desired slip; others are eflective only in relatively large amounts so that use thereof Patented July 29, 1969 increases the manufacturing cost of the cans too greatly; still others fail to give good slip at the higher temperatures to which the tube is subjected when it is exposed to heat developed by friction on the mandrel; or they do not have the hardness necessary to protect the barrier material from galling.

Specifically, one of the methods used to reduce the friction between a steel mandrel and a vinylidene chloride polymer coated paper web was to apply a lubricant to the coating as the coated web was wound on the mandrel. Various water solutions and oils were applied, but these materials built up on the mandrel and resulted in streaks, galling, and oversized can bodies. Another method was to top coat the vinylidene chloride polymer coating with a slippery material such as wax, oil, and soap. Many of the oil additives, floor waxes buffed and unpolished, metal stearate soaps, and silicone oils were fuond to increase the friction as measured by the angle indicative of the coefiicient of friction.

The angle indicative of the coefiicient of friction was measured in the following manner. A steel block weight was used which was 1.9 inches in height, 2 inches in width, and 4 inches in length, having at each end of the bottom a step 1 inch in length, 2 inches in width, and 0.25 inch in height, which was the surface in contact with the slip coated sheet being tested. The weight of the block was 4 pounds or 1 pound per square inch in the horizontal position. The slip composition was coated on kraft paper or similar type of paper and dried. The coated paper was attached to a smooth wooden board with Scotch tape with the uncoated side of the paper adjacent to the wooden board. The weight was placed on the coated surface of the paper, and the board was slowly tilted until slippage occurred. This angle was recorded as an indication of the static coefficient of friction.

In measuring the angle indicative of the kinetic coefficient of friction, the board was raised to a predetermined angle and the weight was then placed on the coated surface of the paper, and the weight was observed to see if slip occurred. The angle of the board was then changed in the proper direction, and the weight again was placed on the coated surface. The angle at which the weight slipped was reported as an indication of the kinetic coefiicient of friction.

It is a principle object of the present invention to provide a composition which is particularly useful as a slip agent in the preparation of spiral-wound paper cans and which overcomes the defects of the slip agents of the prior art.

The novel composition of the present invention comprises a solution or emulsion of a long-chain fatty amide, e.g., oleyl amide. The term fatty amide" as used herein is intended to refer to the neutral derivative of the re-, action of fatty acids and ammonia.

The fatty acid amides employed in the present invention are Water-insoluble solids with a relatively high melting point e. g., in exces of 70 C. (closed tube). The compounds are aliphatic amides with a carbon chain of 14 to 22 atoms. It should be understood that the term fatty acid amide as used herein is intended to include both saturated and unsaturated fatty amides and blends of amides. A particularly preferred fatty amide composition contains at least percent oleyl amide.

The novel slip agents of the present invention are employed either as solutions or emulsions. The solvents employed are organic solvents for the fatty amide, e.g., toluene, chloroform and acetone.

The emulsifiers employed in the present invention are known to the art. Particularly preferred emulsifiers are the partial esters of fatty acids and hexitol anhydrides and polyoxyethylene derivative of partial esters of fatty acids and hexitol anhydrides. As examples of such emulsifiers, mention may be made of the Spans and Tweens, respectively, (trademarks of the Atlas Powder Company, Wilmington, Del.). In a preferred embodiment, a combination of sorbitan monostearate and polyoxyethylene sorbitan monostearate is employed.

In an alternative embodiment, the fatty amide is dissolved in a suitable organic solvent for the amide and employed in a solution form.

The slip composition of the present invention is preferably formulated at a total solids content of about 20 percent and is then diluted with water for employment at a total solids content of about 5 percent. For storage or shipping purposes, the slip composition is prepared at a total solids of 45 percent and then diluted prior to application to the substrate.

When used in an emulsion, the solids are composed of about 70 to 85 percent by weight of a fatty amide and sufficient emulsifier to prepare a stable water emulsion. In a preferred embodiment, the composition contains 80 percent of fatty amide.

The emulsions are prepared by adding a mixture of the fatty amide, a solvent for the fatty amide, e.g., toluene, and at least a portion of the emulsifier system to water containing a small amount of ammonium hydroxide. It is necessary that the components be heated to a least 75 C. prior to mixing, and agitation must be applied during the combining of the materials with the water phase. Agitation is continued until the composition is at room temperature. If dilution of the system is required, both the composition and the diluting Water must be heated to at least 75' C.

The method of depositing a coating of the slip agent on the substrate is not critical. However, if the slip agent is applied in emulsion form, the temperature of the slip agent must be at least 60 C. during the application to the substrate. Any type of coating mechanism or device which is capable of depositing the uniform amount in the desired thickness to the substrate may be employed. Special types which may be used include air knife coater, horizontal and vertical size presses, trailing blade, transfer roll, reverse roll, roller coater, gravure bead coat, metering bar, spray coater, and curtain coater. Deposition may be carried out in one or a number of application, and the amount deposited is such as to provide a dry weight coating ranging between about 0.1 to 1.0 pound per 3,000 square feet of substrate. Dry weight coating ranging from about 0.2 to 0.5 pound per 3,000 square feet are particularly satisfactory. The slip coated substrate is then dried either in air or a suitable drying apparatus. Air drying can be accomplished in less than minutes while oven drying can be effected within 10 to 30 seconds at an oven temperature of 120 to 130 C. The dried slip coating is odorless, clear, and very glossy. The following nonlimiting examples illustrates the preparation of novel compositions within the scope of the present invention.

EXAMPLE 1 Parts by wt. Oleyl amide (Adogen 73Archer Daniels Midland) 80 Toluene 20 Sorbitan monostearate (Span 60-Atlas Powder Com- The above materials were mixed and then heated to 70 C. until clear. Maintaining the mixture at 75 C., it was added to the following mixture:

Ammonium hydroxide 5 high speed, high shear mixer. Mixing was continued at Example A 7 An aqueous vinylidene chloride copolymer emulsion (Daran 210) was coated on one side of a large piece of flexible paperboard of the type used in forming spiralwound paper containers. The paperboard was about 17 mils thick.

The following art typical properties of the vinylidene chloride copolymer emulsion:

Total solids -4-.. About 60%. Color Cream white. Freezing point 36 F.

Particle size .13 avg. (micron). Specific gravity 132030.015.

The polymer emulsion (Daran 210) was applied to the paperboard with a roller and then levelled with a No. 6 Mayer rod. The coated paperboard was initially dried by passing it under infra red lights and then through an oven maintained at 250 F. The dried coated paperboard was then passed again under the infra red lights tofuse the dried vinylidene chloride polymer coating. The web speed was 350 feet per minute. The weight of the dried coating was approximately 8 pounds per ream (3,000 sq. it).

A second coating of the vinylidene chloride polymer emulsion (Daran 210) was applied to the dried coating in the same manner except that a No. 4 Mayer rod was used and that drying temperatures of the first and second zones of the oven were maintained at 300 F. The weight of the dried coating was approximately 2.8 pounds per ream (3,000 sq. ft.). A third coating of the vinylidene chloride polymer emulsion was applied in the same manner as the second coating, and the coating weight was approximately 3.6 pounds per ream (3,000 sq. ft.). The total weight of the coating was approximately 14.4 pounds per ream (3,000 sq. ft.), and the total thickness of the paperboard and the coating was about 18 mils. The vinylidene chloride polymer coating was colorless, clear, smooth, continuous, and glossy.

The slip composition of Example 1 was applied to the above-described coated paper with a roller and then levelled with a Mayer rod. The temperature of the composition was 60 C. The slip coated paperboard was initially dried by passing it under infra red lamps and then through an oven maintained at 300 F. The slip coating was clear, colorless, and glossy.

. Table 1 illustrates the slip characteristics of the composition of Example 1. In addition to determininng the slip characteristics at room temperature, the kinetic angle was also determined at 260 F.

TABLE 1 Room temperature 260 F. Mayer rod N0. Static angle Kinetic angle kinetic angle EXAMPLE 2 A slip composition was prepared by dissolving oleyl amide (4 percent-by weight based on the Weight of amide and solvent) in toluene.

The slip coat of Example 2 was applied to coated paper in the same manner as described in Example A. The slip coating was clear, colorless and glossy.

Table 2 illustrates the slip characteristics of the composition of Example 2. A control, toluene alone applied to the coated paper in the same manner, was also measured for slip characteristics.

TABLE 2 Mayer rod No.

Static angle Kinetic angle Control Example 2 As stated above, the emulsion system containing the fatty amide is particularly preferred because of the ease of application, i.e., conventional equipment is employed rather than the explosion-proof equipment and solvent recovery systems which would be necessary with solutions of the fatty amide. The emulsion systems also provide superior slip characteristics.

As well as the advantageous slip characteristics which are achieved using the novel composition of the present invention, it has also been found that heat sealing characteristics of the coated paper are improved by the novel composition of the present invention. Contrary to what would be expected with the composition of this invention, a better heat seal is obtained in a shorter time and at a lower temperature when the slip coat is employed. In general, the heat sealing temperature of the coated paper is lowered about 25 F.

Although the novel slip composition of the present invention has been described primarily in terms of use with paper coated with vinylidene chloride polymer, the compositions are also used satisfactorily on polyethylene and polypropylene to provide the desired degree of slip.

The novel compositions of the present invention have been used on coated paper which was formed into spiral- Wound cans on a mandrel at 300 feet per minute at F. without jamming, galling or other indications of excessive friction.

What is claimed is:

1. An article comprising a paper substrate, a moisture resistant film of polymer selected from the group consisting of vinylidene chloride polymers, polyethylene and polypropylene superimposed on said substrate and a slip coating on said film, said slip coating consisting essentially of a C to C fatty amide, the amount of said slip coating on said film ranging between about 0.1 to 1 pound per 3,000 square feet of said substrate.

2. An article as defined in claim 1 wherein said moisture-resistant film is a vinylidene chloride copolymer film.

3. An article as defined in claim 1 wherein said slip coating additionally contains as an emulsifier a minor amount of the partial ester of a fatty acid and hexitol anhydride and polyoxyethylene derivative of the partial esters of a fatty acid and hexitol anhydride.

4. An article as defined in claim 1 wherein said fatty amide is oleyl amide.

References Cited UNITED STATES PATENTS 2,565,403 8/1951 Sproule et al. 3,132,041 5/1964 Pihl. 3,200,005 8/1965 Bauer.

FOREIGN PATENTS 531,497 1/1941 Great Britain.

WILLIAM D. MARTIN, Primary Examiner R. HUSACK, Assistant Examiner US. Cl. X.R. 

